Vertical Deformation Rates Research Articles

A novel ultrasonic rolling assisted direct energy deposition method with semi-solid thixo-forming characteristics for AA6061

In order to overcome the defects during the process of additive manufacturing for AA6061, a novel ultrasonic rolling assisted direct energy deposition method with semi-solid thixo-forming characteristics was proposed in this study, which used cold deformed AA6061 wire as raw material, and a corresponding process platform was established. The results showed that under the conditions of laser heating temperature of 750 ℃ and heating plate temperature of 200 ℃, the sample could achieve continuous multi-pass deposition while retaining some of the cold-drawn plastic deformation energy. When the vertical deformation rate was 0.153 and the ultrasonic amplitude was 20 μm, the microstructure of deposition sample after semi-solid heat-treat exhibited typical equiaxed grain characteristics, corresponding to average grain diameter of 95.6 μm and shape coefficient of 1.263. Thin-walled samples with different shapes were formed to verify the capability of process platform. The inference of the formation mechanism of semi-solid microstructure was revealed at last: the introduction of ultrasonic rolling supplemented the plastic deformation energy, and semi-solid heat-treat provided temperature and time for the incubation of equiaxed grains, both of which were crucial for the formation of the semi-solid microstructure.

Study on InSAR deformation information extraction and stress state assessment in a railway tunnel in a plateau area

Introduction: The study proposes a method for evaluating stress distribution in high-altitude Tibetan Plateau railway tunnels using high-precision radar satellite time-series interferometric synthetic aperture radar technology.Methods: To effectively monitor and prevent geological hazards during the construction process, this method i employed, as it serves as a component of advanced geological prediction and surrounding rock deformation monitoring technology for high-altitude tunnels, particularly in the Dongelu Tunnel of the China–Tibet Railway. The study utilizes time-series interferometric synthetic aperture radar to obtain deformation information for Dongelu Tunnel area between 2022 and 2023 from Sentinel- 1A orbit images. This quantitatively investigates the upper mountain body and line-of-sight direction along the tunnel. The deformation characteristics are correlated with high-frequency and high-precision automated vertical displacement monitoring results, determining the spatiotemporal distribution of tunnel deformation. In this study, a model that determines the vertical stress state of the Dongelu Tunnel under loading near the entrance and evaluates its health status was established.Results: The results show that the surface deformation of the mountain above the tunnel axis develops slowly and is relatively small, with a maximum vertical deformation rate of 1–3 mm/year. The average stress on the tunnel arch is 5.54 MPa, with a fluctuation range of 0.01 MPa. Temporal Q9 changes in various parts of the tunnel are periodic, with maximum fluctuations observed in December 2022. The study reveals inconsistent surface settlement of the tunnel arch and mountain above it, causing minor vertical stress changes. As the tunnel construction progresses, vertical stress variation shows periodicity because of an initial imbalance in internal stress within the mountain. Stress fluctuations near the tunnel entrance occur during the initial excavation phase, gradually diminishing as the project progresses and internal stress stabilizes.Discussion: The proposed tunnel monitoring and stability assessment method can reduce its impact on engineering construction and provide guidance for advanced geological prediction.

Estimation of surface deformation in Sikkim and Eastern Nepal Himalaya using PSInSAR technique

The region of the Himalayan arc covering Sikkim and eastern Nepal experiences dominant strike-slip deformation oblique to the convergence direction of the Indian plate. This region is also traversed by transverse structural and tectonic features. The present study is aimed at comprehending the horizontal and vertical deformation rates for this region using the PSInSAR technique. We utilized 70 and 78 Single Look Complex images in ascending and descending passes respectively, spanning from February 2017 to August 2023 for time-series displacement measurement along the radar line of sight (LOS). The results reveal the LOS velocity ranging from −15 to +10 mm/yr for the ascending data and ±20 mm/yr for the descending data. The mean line-of-sight velocities of ascending and descending passes were decomposed to estimate the horizontal (east-west) and vertical components of the deformation vector. These components range from ±15 mm/yr and −12 to +8 mm/yr, respectively, suggesting that the horizontal deformation predominates in the study area. A NW-SE trending boundary coinciding with the Tista lineament sub-divides the study region into the eastern Nepal and the Sikkim blocks based on the patterns of the deformation rates. The eastern Nepal block south of the Main Central Thrust exhibits locked portion of the arc with eastward motion, whereas the Sikkim block exhibits uplift (unlocked with creep) and westward motion. The amplitudes of these deformation rates support dominant strike-slip deformation with minor vertical deformation component. These results suggest that the Tista lineament is a prominent strike-slip fault and probably the most significant active tectonic feature in the region. Together with the seismicity data, we infer that probably the entire crustal block rather than the Himalayan wedge is contributing to the surface deformation, as mapped by the present PSInSAR study.

Pleistocene valley incision, landscape evolution and inferred tectonic uplift in the central parts of the Balkan Peninsula – Insights from the geochronology of cave deposits in the lower part of Crna Reka basin (N. Macedonia)

Although the general geomorphology is reasonably well understood, not much information is available on the incision rates of rivers and related tectonic uplift in the central parts of the Balkan Peninsula. Caves in the lower part of Crna Reka drainage (N. Macedonia) provide the possibility to reconstruct the Neogene-Quaternary evolution of this area, as previous research has identified two major cave development phases: one related to Pliocene-Early Pleistocene basin infilling and establishment of lacustrine environments, and a subsequent cave development phase related to valley incision due to draining of the lacustrine systems and tectonic uplift.Here, we present new geochronological data obtained by U-Th dating on speleothems and cosmogenic nuclide burial age determination of clastic cave sediments, that provide time constraints on the Pleistocene karst and valley evolution, and an insight into the related tectonic uplift. The obtained cosmogenic nuclide burial age (2.1 ± 0.5 Ma) of the clastic cave sediments from Temna Peštera – Dragožel, further supports previous results on placing the onset of the draining of the Pliocene lakes in Macedonia in the Early Pleistocene. The similar timing obtained for the downstream and upstream parts of Crna Reka drainage suggests that the draining was more likely initiated by regional uplift, rather than headward erosion related to subsidence in the Aegean Sea. The Middle to Late Pleistocene age of the dated speleothems agrees well with the existing conceptual model for karst and landscape evolution in the area. The cumulative valley incision rates based on these radiometric data show an increase towards the present, with values of <0.1 m/ka in Early Pleistocene, increasing to ∼0.2–0.5 m/ka in Middle Pleistocene, and up to 1 m/ka in Late Pleistocene. They are lower than the measured uplift rates in the area (1.1–1.2 m/ka), and mostly overlap with the range of GPS-based vertical deformation rates in the Hellenides. Higher Middle to Late Pleistocene uplift rate is inferred in the downstream part of Crna Reka, an area in the Vardar zone bounded by seismogenic faults, than in the upstream part, at the easternmost edge of the Pelagonian massif.

Correlation analysis of longitudinal cracks and vertical deformation within asphalt pavement of cold regions

The asphalt pavement longitudinal crack is a common distress in cold regions, resulting from uneven deformation of the subgrade. Analysis of the correlation law between uneven deformation and crack distress is of positive significance for understanding the mechanism of crack initiation, and putting forward treatment measures. In view of the complexity of longitudinal crack inducement and road surface deformation, the grey relational method was used to analyze this relationship. Through long-term monitoring of the vertical deformation data of typical road sections, the vertical deformation law of the pavement surface and its deformation characteristics under the action of temperature field are analyzed. Parameters such as vertical relative deformation, vertical relative deformation rate and vertical differential deformation VDSr were constructed to describe vertical deformation characteristics. Typical distribution characteristics of longitudinal fractures and their length and distribution characteristics are also described. The grey correlation analysis theory was utilized to analyze the relationship between deformation characteristics of sections, cross sections and monitoring points and longitudinal crack characteristics (length and location). The analysis reveals a linear positive correlation or a high correlation between several indicators. This study can provide a deeper understanding of the occurrence and development mechanism of longitudinal cracks in asphalt pavement of cold areas, and give references for the research of road engineering structure, materials and distress prevention.

Contribution Factor Analysis of the Wuhan Yangtze River Bridge Deformation Using Sentinel-1A SAR Imagery and In Situ Data

Bridges play a crucial role in the development of the national economy and transportation industry, and their deformation monitoring is vital for ensuring their health. Therefore, it is necessary to conduct long-term monitoring of bridges’ deformation. This study monitored the deformation of the Wuhan Yangtze River Bridge using the SBAS-InSAR technology and Sentinel-1A data. The deformation results were analyzed in combination with bridge structure, human activity, temperature and stratigraphy. The results were as follows: (1) The vertical deformation rate of the bridge was between −15.6 and 10.7 mm/year, and part of the deformation belonged to rebound deformation; (2) The middle span deformation is the largest and the uplift and lowering alternate; (3) The reduction in human activity is the reason for the lower deformation amplitude from January to October 2020 compared to after October 2020; (4) A positive correlation between deformation and temperature was observed only along a portion of the bridge; (5) There is no direct correlation between observed lowering and stratigraphy under the bridge piers, as the sinking is presumably absorbed by the bridge structure.

Integration of Sentinel–1 and Landsat–8 data for identifying deformation risk of hydraulic engineering in seasonally frozen salinization regions

Hydraulic engineering has positive effects on agricultural production and soil desalination. However, freeze–thaw cycles can cause instability in canal slopes, emphasizing the need for effective deformation monitoring. Using Sentinel-1B data acquired from November 2017 to August 2019 and applying the small baseline subset (SBAS) InSAR method, two unstable canal segments with vertical deformation rates exceeding –40 mm/year were identified in Songyuan, Northeast China. The canal slopes uplifted in winter and experienced accelerated subsidence in spring, with the shady slope experiencing a deformation rate approximately 10 mm/year faster than the sunny slope. Further investigation, integrating Landsat–8 data collected from November 2017 to August 2019, revealed that the shady slope received less thermal radiation than the sunny slope, with an average annual temperature difference on the land surface of approximately 1 ℃. In winter, the saline–alkali soil particles formed a thick unfrozen water film, which, driven by temperature and soil–water gradients, migrated towards the freezing front, froze, and caused soil frost heave. The shady slope experienced longer freezing periods and deeper frozen depths, up to 240 cm, causing more unfrozen water migration and greater uplift deformation than the sunny slope. In spring, as temperature rose, the soil thawed from the surface downward. Notably, the shady slope thawed at a slower rate than the sunny slope, forming a frozen lens near a depth of 100 cm. Frozen lens acted as a barrier for meltwater infiltration, impeding the dissipation of pore water pressure, making the shady slope prone to surface landslides. The integration of multiple data sources is beneficial for identifying deformation risk in hydraulic engineering.

Monitoring and analysis of surface deformation in alpine valley areas based on multidimensional InSAR technology

Joshimath has received much attention for its massive ground subsidence at the beginning of the year. Rapid urbanization and its unique geographical location may have been one of the factors contributing to the occurrence of this geological disaster. In high mountain valley areas, the complex occurrence mechanism and diverse disaster patterns of geological hazards highlight the inadequacy of manual monitoring. To address this problem, the inversion of deformation of the Joshimath surface in multiple directions can be achieved by multidimensional InSAR techniques. Therefore, in this paper, the multidimensional SBAS-InSAR technique was used to process the lift-track Sentinel-1 data from 2020 to 2023 to obtain the two-dimensional vertical and horizontal deformation rates and time series characteristics of the Joshimath ground surface. To discover the causes of deformation and its correlation with anthropogenic activities and natural disasters by analyzing the spatial and temporal evolution of surface deformation. The results show that the area with the largest cumulative deformation is located in the northeastern part of the town, with a maximum cumulative subsidence of 271.2 mm and a cumulative horizontal movement of 336.5 mm. The spatial distribution of surface deformation is based on the lower part of the hill and develops towards the upper part of the hill, showing a trend of expansion from the bottom to the top. The temporal evolution is divided into two phases: gentle to rapid, and it is tentatively concluded that the decisive factor that caused the significant change in the rate of surface deformation and the early onset of the geological subsidence hazard was triggered by the 4.7 magnitude earthquake that struck near the town on 11 September 2021.

Preliminary Study on InSAR-Based Uplift or Subsidence Monitoring and Stability Evaluation of Ground Surface in the Permafrost Zone of the Qinghai–Tibet Engineering Corridor, China

Against the background of global warming, permafrost areas are facing increasing thawing, and the threat to the surface of the Qinghai–Tibet Engineering Corridor (QTEC) is serious. It is imperative to understand the current surface deformation and analyze the changes spatiotemporal characteristics for future warnings. At present, observation of a long time series and overall coverage of vertical ground deformation in QTEC are lacking. This paper takes the permafrost deformation of the QTEC as its research object. It uses the pretreated LiCSAR product and combines it with the LiCSBAS package to obtain monitoring results of the long time series deformation of the engineering corridor’s surface. The SAR image acquisition date is taken as the constraint, the results covering the whole processing area are selected, and then the vertical deformation information covering the entire engineering corridor area by ignoring the north–south displacement is calculated. The results show that the surface of the study area, as a whole, slightly subsided between May 2017 and March 2022, and the vertical deformation rate was mostly distributed at −27.068 mm/yr − 18.586 mm/yr, with an average of −1.06 mm/yr. Vertical deformation dominated at 52.84 percent of the study area, of which settlement accounted for 27.57 percent and uplift accounted for 25.27 percent. According to the statistics of the normal distribution of deformation velocity per pixel, a total of 77% of the engineering corridor was stable, with a vertical deformation rate between −6.964 mm/yr and −4.844 mm/yr, and 17.7% of the region was sub-stable, with a settling rate of −12.868 mm/yr − –6.964 mm/yr. The unstable regions included areas with settlement rates greater than 12.868 mm/yr and uplift rates greater than 10.748 mm/yr, representing 4.4 percent and 0.9 percent of the total area, respectively, for a total of 5.3 percent. The results of this paper can be used as the theoretical basis and as basic data for decision making and scientific research in various departments, and they are of great significance for surface stability assessment and early warnings along engineering corridors and traffic projects.

Application of direct coupling method to design problems of hydrostatic guideways accounting for fluid-structure interactions

The deformation of slide carriages caused by oil pressure produces a substantial effect on the performance of hydrostatic guideways. This paper is aimed to propose a practical fluid-structure interaction (FSI) model adopting the direct coupling method to predict the performance more efficiently. To this end, the full-size model containing elastic deformation and thin film pressure fields is solved simultaneously, and the specific boundary conditions caused by the orifice are considered and enforced via the root iterative method. The model is confirmed to be mesh-independent by meshing with three different densities. Furthermore, the vertical stiffness, deformation, and flow rate of the hydrostatic guideway are evaluated and tested with various oil supply pressures. Compared with the theoretical values without considering deformation, the simulation results take the structural deformation into account and thereby exhibit good agreement with those of the experiment. Based on the proposed FSI model, the orthogonal design method is also employed to analyze the influence of structure geometry, and the carriage slide thickness is introduced as the key influential factor of stiffness.

RETROSPECTIVE STUDY OF VERTICAL GROUND DEFORMATION IN COMO, NORTHERN ITALY: INTEGRATION OF LEVELLING AND PSI MEASUREMENTS

Abstract. Subsidence-related vertical ground deformation due to natural and anthropogenic factors may lead to considerable damages to structures and infrastructures, and may increase the occurrence probability of consequential events, such as floods, especially on sea and lake shores. Como city, placed in the north of Italy, adjacent to Como Lake, is subjected to significant subsidence phenomenon, which has been monitored by geodetic levelling networks. In this work the historical geodetic levelling measurements and satellite-based Synthetic Aperture Radar (SAR) data archive are integrated to assess the accuracy of Atmospheric Delay and Deformation Rate estimations obtained through Persistent Scatter Interferometry (PSI) techniques. Tree levelling measurement datasets acquired in 1990, 1997 and 2004 are used in order to obtain the precise deformation rate at the benchmarks for two periods of 1990–1997 and 1997–2004. For multi-temporal InSAR analysis, 106 SAR images (1992–2004) and 41 SAR images (1992–2004) in Ascending Track orbit from ERS-1/2 missions are used in this study. The assessment is performed through a statistical comparison between two sets of vertical land deformation rates obtained by integrated methods. The results of the validation represented a good consistency between deformation rates derived by both techniques. Also, this study has revealed the potential of SAR images acquired in gyro-less mode by ERS-2 mission (2001–2004) in terms of the estimation of ground deformation.

Mapping Tunneling-Induced Uneven Ground Subsidence Using Sentinel-1 SAR Interferometry: A Twin-Tunnel Case Study of Downtown Los Angeles, USA

Synthetic Aperture Radar (SAR) interferometry is a formidable technique to monitor surface deformation with a millimeter detection resolution. This study applies the Persistent Scatter-Interferometric Synthetic Aperture Radar (PSInSARTM) technique to measure ground subsidence related to a twin-tunnel excavation in downtown Los Angeles, USA. The PSInSARTM technique is suitable for urban settings because urban areas have strong reflectors. The twin tunnels in downtown Los Angeles were excavated beneath a densely urbanized area with variable overburden depths. In practice, tunneling-induced ground settlement is dominantly vertical. The vertical deformation rate in this study is derived by combining Line of Sight (LOS) deformation velocities obtained from SAR images from both ascending and descending satellite orbits. Local and uneven settlements up to approximately 12 mm/year along the tunnel alignment are observed within the allowable threshold. No severe damages to aboveground structures were reported. Furthermore, ground movements mapped one year before tunnel construction indicate that no concentrated ground settlements pre-existed. A Machine Learning (ML)-based permutation feature importance method is used for a parametric study to identify dominant factors associated with the twin-tunneling induced uneven ground subsidence. Six parameters are selected to conduct the parametric study, including overburden thickness, i.e., the thickness of artificial fill and alluvium soils above the tunnel springline, the distance between the two tunnel centerlines, the depth to the tunnel springline, building height, the distance to the tunnel, and groundwater level. Results of the parametric analysis indicate that overburden thickness, i.e., the thickness of artificial fill and alluvium soils above the tunnel springline, is the dominant contributing factor, followed by the distance between tunnel centerlines, depth to the tunnel springline, and building height. Two parameters, the distance to the tunnel, and the groundwater level, play lesser essential roles than others. In addition, the geological profile provides comprehension of unevenly distributed ground settlements, which are geologically sensitive and more concentrated in areas with thick artificial fill and alluvium soils, low tunnel depth, and high groundwater levels.

Nearly Three Centuries of Lava Flow Subsidence at Timanfaya, Lanzarote

AbstractThe 1730–1736 eruption on Lanzarote was one of the most significant volcanic eruptions to occur on the Canary Islands, with lavas covering over 200 km2. Globally, it is volumetrically the third largest known subaerial basaltic fissure eruption in the past 1,100 years. Here we use Sentinel‐1 and ENVISAT interferograms on both ascending and descending orbits to construct a time series of line‐of‐sight surface displacements and calculate linear vertical deformation rates. We resolve a constant subsidence rate of about 6 mm/yr associated with an area of ∼20 km2 within the central and western portion of the Timanfaya lava flows relative to the rest of the island. This is consistent over the 28‐year period (1992–2020) covered by the Sentinel‐1 and ENVISAT data when combined with the previously published European Remote‐Sensing Satellite data. Time series constructed using Sentinel‐1 short interval interferograms have previously been shown to suffer systematic biases and we find that by making longer period interferograms these biases can be mitigated (when compared against an averaged stack of 1‐year interferograms). Cooling‐driven contraction of an intrusion would require improbably large sill thickness to achieve the observed subsidence rates. Our observations are consistent with the cooling of lavas on the order of one hundred meters, twice as thick as previous estimates, which suggests overall lava volume for this eruption may have been underestimated. This is also evidence of the longest duration of lava flow subsidence ever imaged which indicates that these cumulative thick flows can continue to deform significantly even three centuries after emplacement.

Integration of Vertical and Horizontal Deformation Derived by SAR Observation for Identifying Landslide Motion Patterns in a Basaltic Weathered Crust Region of Guizhou, China

In recent years, due to adverse geological conditions, intense human engineering activities, and extreme weather conditions, catastrophic landslides have frequently occurred in southwest China, causing severe loss of life and property. Identifying the kinematic features of potential landslides can effectively support landslide hazard prevention. This study proposes a remote sensing identification method for rotational, planar traction, and planar thrust slides based on geomorphic features as well as vertical and slope-oriented deformation rates. Rotational landslides are characterized by similar vertical and horizontal deformation rates, with vertical deformation mainly occurring at the head and gradually decreasing along the slope, while horizontal deformation mainly occurs at the foot and gradually increases along the slope. As for the planar slide, the dominant deformation is in the horizontal direction. It is further classified into the planar traction and planar thrust types according to the driving position. The vertical deformation of planar traction slides is concentrated at the foot, while the vertical deformation of planar thrust slides is concentrated at the head of the landslide. We identified 1 rotational landslide, 10 planar traction landslides and 10 planar thrust landslides in the basalt weathering crust area of Guizhou. Field investigations of three landslides verified the method’s accuracy. Combining two-dimensional rainfall and time-series deformations, we found that there is a significant positive correlation between landslide deformation acceleration and precipitation. The landslide kinematic identification method proposed in this paper overcomes the shortcomings of the inability to accurately characterize landslide motion by line-of-sight displacement and realizes the non-contact identification of active landslide motion patterns, which is an essential reference value for geological disaster prevention and control in the study area.

Analysis of regional large-gradient land subsidence in the Alto Guadalentín Basin (Spain) using open-access aerial LiDAR datasets

Land subsidence associated with groundwater overexploitation in the Alto Guadalentín Basin (Spain) aquifer system has been detected during the last decades. In this work, for the first time, we propose a new point cloud differencing methodology to detect land subsidence at basin scale, based on the multiscale model-to-model cloud comparison (M3C2) algorithm. This method is applied to two open-access airborne LiDAR datasets acquired in 2009 and 2016, respectively. First the internal edge connection errors in the different flight lines were addressed by means of a smoothing point cloud method. LiDAR datasets capture information from ground and non-ground points. Therefore, a method combining gradient filtering and cloth simulation filtering (CSF) algorithms was applied to remove non-ground points. The iterative closest point (ICP) algorithm was used for point cloud registration of both point clouds exhibiting a very stable and robust performance. The results show that vertical deformation rates are up to −14 cm/year in the basin from 2009 to 2016, in agreement with the displacement reported by previous studies. LiDAR results have been compared to the velocity measured by continuous GNSS stations and an InSAR dataset. For the GNSS-LiDAR and InSAR-LiDAR comparison, we computed a common 100 × 100 m grid in order to assess any similarities and discrepancies. The results show a good agreement between the vertical displacements obtained from the three different surveying techniques. Furthermore, LiDAR results were compared with the distribution of compressible soil thickness showing a clear relationship. The study underlines the potential of open-access and non-customized LiDAR to monitor the distribution and magnitude of vertical deformations in areas prone to be affected by groundwater-withdrawal-induced land subsidence.

Analysis of the common model error on velocity field under Colored noise model by GPS and InSAR: A case study in the Nepal and everest region

The accuracy of the velocity field will be affected by the noise model and common mode errors through GPS time series analysis. In order to analyze the influence of these two factors on the accuracy of the velocity field, two kinds of data are used, including the three-year observation from 20 permanent GPS stations with high spatial correlation in the Everest, which is about 650 km from north to south and 1068 km from east to west, and three-year 80 ascending images and 141 descending images from sentinel-1A, which are processed by GAMIT/GLOBK software and Small Baseline Subset-Interferometric Synthetic Aperture Radar method (SBAS-InSAR), respectively. The vertical deformation rate is solved by time series analysis through a self-made adaptive algorithm. In the analysis, the linear change rate, period, half period coefficient, and residual sequence of all stations are solved by using James L. Davis periodic model. The noise type of residual sequence is analyzed by the power spectrum model. The spatio-temporal correlated noise, Common Mode Error (CME), is extracted by the Principal Component Analysis (PCA) and Karhunen-Loeve (KLE) methods. The results show that noises can be best described by “flicker noise + white noise” model. After the removal of CME, the R2 estimates of all stations are above 0.8, with RMS value of velocity field decreasing from 1.428 mm/yr to 1.062 mm/yr and 1.063 mm/yr to 0.815 mm/yr, in N and E directions, respectively, indicating that the influence of CME can't be ignored in the extraction of the high-precision velocity field in the Nepal and Everest region.

Late Quaternary Slip Rate of the Zihong Shan Branch and Its Implications for Strain Partitioning Along the Haiyuan Fault, Northeastern Tibetan Plateau

AbstractGeometrical complexities such as bends and branches are ubiquitous along strike‐slip faults. Understanding strain partitioning between the different fault strands along such sections is key to assessing kinematics and evolution through time of a fault system and related seismic hazards. The Haiyuan fault, one of the longest strike‐slip faults of the Tibetan Plateau, has developed a multi‐stranded complex fault geometry along the Hasi Shan restraining bend. In this study, we quantified the slip rate of the ∼50‐km‐long Zihong Shan fault, which is the poorly‐known southernmost fault strand of the Hasi Shan restraining bend. We computed high‐resolution DEMs and orthophotos to document the offset landforms along this fault using drone surveys. At selected sites with well‐preserved offset geomorphic markers, we quantified displaced terraces and channels using microtopography analysis. We dated the abandonment age of these terraces using 10Be cosmogenic depth profiles and OSL dating techniques. It yields a left‐lateral slip rate of 1.9 ± 0.6 mm/yr since ∼13 ka, which is similar to the rate of the main Hasi Shan branch that ruptured during the 1920 Haiyuan earthquake. The minimum total horizontal slip rate system summed over the multiple strands of the Haiyuan fault at the Hasi Shan restraining bend is 4.1 ± 0.6 mm/yr, without considering the vertical deformation rate of these fault strands. The rate is thus slightly smaller than, but comparable to, slip‐rates determined along the rest of the Haiyuan fault, east and west of the Hasi Shan restraining bend.

The Current Crustal Vertical Deformation Features of the Sichuan–Yunnan Region Constrained by Fusing the Leveling Data with the GNSS Data

This study uses the least squares collocation method to fuse the leveling vertical deformation velocity in the Sichuan–Yunnan region with the GNSS observations of this region from 320 stations in the China Crustal Movement Observation Network (CMONOC) and the China Continental Tectonic Environment Monitoring Network (CMTEMN) from 1999 to 2017. Such fusion is to improve the accuracy of the vertical deformation rates in large spatial scales. The fused vertical deformation results show that: (1) the fused deformation field has a uniform spatial distribution, and shows detailed change characteristics of key regions; (2) the current vertical crustal motion in this region is featured by the contemporaneous occurrence of crustal compression, shortening and uplift and basin extensional subsidence; (3) most areas in this region experience uplifts, as the lateral push of the Qinghai–Tibet Plateau was blocked by the Sichuan Basin. The areas on the northwest side of the Longmenshan fault and the Lijiang-Xiaojinhe fault are dominated by uplifts, with the velocity of 1.5 mm/a–5.5 mm/a, and the region on the southeast side has slight uplifts, with the velocity of 1.0 mm/a–1.5 mm/a; (4) many areas have high gradient vertical deformation, especially the region close to the Wenshan fault and on the two sides of the Yarlung Zangbo fault that has the value of 3.0–4.0 × 10−8/a, deserving further attention to be paid to the long-term earthquake hazards.

Monitoring and analysing long-term vertical time-series deformation due to oil and gas extraction using multi-track SAR dataset: A study on lost hills oilfield

The Lost Hills oilfield, located ∼70 km northwest of Bakersfield in the San Joaquin Valley, has a long history of oil/gas extraction, and it suffers from long-term ground deformation. Many SAR datasets include information about the Lost Hills oilfield over the past two decades. This study focused on calculating and analysing the long-term vertical ground deformation due to oil and gas extraction in the Lost Hills oilfield and proposed a new strategy inspired by the “Small Baseline Subset” idea for jointly processing multi-track SAR images to obtain long-term time-series deformations. The experimental results showed a maximum vertical deformation rate of 20 mm/year in the uplift region and –90 mm/year in the subsidence region of the Lost Hills field from August 1995 to September 2010, and the long-term vertical time-series deformations had a precision of 5 mm. In addition, a multivariate polynomial regression model was used to quantify the relationship between surface deformation volume changes and water, oil, and gas injection-production data. The results demonstrated that the relationship between the ground volume change and injection/production dataset in the subsidence region followed a multivariate linear model, whereas the uplift region satisfied a multivariate quadratic polynomial model. The modelling results provided a new perspective on interpreting ground deformation due to oil/gas extraction.

Late Quaternary Marine Terraces and Tectonic Uplift Rates of the Broader Neapolis Area (SE Peloponnese, Greece)

Marine terraces are geomorphic markers largely used to estimate past sea-level positions and surface deformation rates in studies focused on climate and tectonic processes worldwide. This paper aims to investigate the role of tectonic processes in the late Quaternary evolution of the coastal landscape of the broader Neapolis area by assessing long-term vertical deformation rates. To document and estimate coastal uplift, marine terraces are used in conjunction with Optically Stimulated Luminescence (OSL) dating and correlation to late Quaternary eustatic sea-level variations. The study area is located in SE Peloponnese in a tectonically active region. Geodynamic processes in the area are related to the active subduction of the African lithosphere beneath the Eurasian plate. A series of 10 well preserved uplifted marine terraces with inner edges ranging in elevation from 8 ± 2 m to 192 ± 2 m above m.s.l. have been documented, indicating a significant coastal uplift of the study area. Marine terraces have been identified and mapped using topographic maps (at a scale of 1:5000), aerial photographs, and a 2 m resolution Digital Elevation Model (DEM), supported by extensive field observations. OSL dating of selected samples from two of the terraces allowed us to correlate them with late Pleistocene Marine Isotope Stage (MIS) sea-level highstands and to estimate the long-term uplift rate. Based on the findings of the above approach, a long-term uplift rate of 0.36 ± 0.11 mm a−1 over the last 401 ± 10 ka has been suggested for the study area. The spatially uniform uplift of the broader Neapolis area is driven by the active subduction of the African lithosphere beneath the Eurasian plate since the study area is situated very close (~90 km) to the active margin of the Hellenic subduction zone.